Francis-type runner for a hydraulic machine, hydraulic machine including such a runner, and method for assembling such a runner

ABSTRACT

The present invention relates to a Francis runner for a hydraulic machine that comprises a belt with a rotational symmetry about a central axis of the runner, a ceiling with a rotational symmetry about the axis, and a plurality of blades ( 2   1   , 2   2 ) extending between the ceiling and the belt. The runner also includes at least two elements ( 41, 42, 43, 61, 62, 63 ) partially defining at least the belt and/or the ceiling while at least one edge ( 23   1   , 23   2   , 24   1   , 24   2 ) of a blade ( 2   1   , 2   2 ) is inserted between the two elements defining the belt and/or the ceiling.

The present invention relates to a Francis-type runner for a hydraulicmachine, to a hydraulic machine comprising such a runner, and to amethod of assembling such a runner.

Within the meaning of the present invention, a hydraulic machine may bea turbine, a pump or a pump turbine, used, for example, in ahydroelectric power station.

The invention relates in particular to a Francis-type runner for ahydraulic machine intended to have a forced flow of water passed throughit. Such a flow has the effect of rotating the runner, when the machineis a turbine. When the machine is a pump, such a flow results from thisrotation.

In the context of a hydraulic machine, it is known practice to useFrancis-type runners that have a band, a crown and blades extendingbetween the band and the crown.

A runner may be of one piece, usually of cast or mechanically weldedconstruction. Because such a runner has imposing overall dimensions, itscost of production is not insignificant. Moreover, the manufacture ofsuch a runner, firstly, requires a known-how which is becomingincreasingly rare and secondly presents health and safety issues becauseof the need to get into the hydraulic passages of the runner in ordernotably to perform the welding and grinding operations.

It is an object of the present invention to provide a runner theproduction of which can be readily industrialized, while at the sametime guaranteeing a satisfactory level of quality.

To this end, the subject of the invention is a Francis-type runner for ahydraulic machine, comprising:

-   -   a band with symmetry of revolution about a central axis of the        runner,    -   a crown with symmetry of revolution about the axis, and    -   a plurality of blades extending between the crown and the band,        characterized in that the runner comprises at least two elements        at least partially defining the band and/or the crown, and in        that at least one edge of a blade is engaged between these two        elements defining the band and/or the crown.

By virtue of the runner according to the invention, its manufacturer isin a position to alleviate the problems associated both with the qualityof the runner and with the production cost and lead time thereof.

According to other advantageous features of the runner according to theinvention, considered in isolation or in any technically feasiblecombinations:

-   -   the lower edge and/or the upper edge of at least one blade lies        flush with the exterior surface of the band and/or of the crown;    -   the runner comprises at least two band elements and two crown        elements, each element being fixed between two adjacent blades        by welding;    -   the runner comprises at least one first subassembly defined by a        first part of the band and a first part of the crown, the two        parts being connected to a first blade, the first subassembly        being cast, and a second subassembly, defined by a second part        of the band and a second part of the crown, the two parts being        connected to a second blade, the second subassembly being cast        and welded to the first subassembly;    -   at least one of the blades comprises two lateral fillets facing        one another and positioned near at least one edge for welding to        the band and/or to the crown;    -   the lateral fillets are machined in the blade;    -   the lateral fillets define a local narrowing.

Another subject of the invention is a hydraulic machine comprising arunner as described hereinabove.

Furthermore, another subject of the invention is a method of assemblinga runner as explained hereinabove. According to this method:

-   -   band elements and/or crown elements are manufactured, and    -   the band elements and/or crown elements are assembled by welding        and/or through casting, with at least one edge of one blade        being engaged between two band elements and/or crown elements.

The invention will be better understood from reading the descriptionwhich will follow, given solely by way of nonlimiting example and madewith reference to the accompanying drawings in which:

FIG. 1 is an axial section through a runner according to the presentinvention;

FIG. 2 is the runner of FIG. 1 viewed from above;

FIG. 3 is, to a larger scale, a part section on III-III of FIG. 2through the runner of FIGS. 1 and 2 while the runner is in the processof being manufactured;

FIG. 4 is a view, to a larger scale, corresponding to detail IV in FIG.3, of a runner according to a second embodiment;

FIG. 5 is a view similar to FIG. 4 in the case of a runner according toa third embodiment;

FIG. 6 is a runner according to a fourth embodiment, viewed from above;and

FIG. 7 is, to a larger scale, a part section on VII-VII of FIG. 4through the runner of FIG. 6 while the runner is in the process of beingmanufactured.

FIGS. 1 and 2 depict a Francis-type turbine runner 1 which rotates abouta vertical axis X-X which is a central axis of the runner 1. A flow Efrom a duct not depicted is intended to pass through the runner 1 in thedirection of a draft tube, not depicted. The runner 1 comprises blades 2which extend between a crown 4 and a band 6. These two bodies 4 and 6have symmetry of revolution about the axis X-X. The blades 2 are evenlydistributed about the axis X-X.

As depicted more specifically in FIG. 2, the nine blades 2, secured tothe crown 4 and to the band 6, are curved. The blades 2 each define aleading edge 21, facing toward the outside of the runner 1, and atrailing edge 22, facing toward the axis X-X.

The runner 1 also comprises a coupling flange 8 for coupling the runner1 to a shaft, not depicted, of the turbine. The flange 8 may be madeeither of sheet metal or as a casting. The flange 8 may then be weldedto the other elements that make up the runner.

As depicted in FIG. 2, the crown 4 comprises nine distinct elements,each separated from the adjacent element by a blade 2. In thecross-sectional view that is FIG. 3, a first element 41 partiallydefines the crown 4. A second 42 and third 43 element of the crown 4 arepositioned one on each side of the element 41. This element 41 isseparated from the two elements 42 and 43 respectively by an upper andinner edge 23 ₁ or 23 ₂ of a first blade 2 ₁ and of a second blade 2 ₂.

In other words, the crown 4 is made up of nine elements 41, 42, 43, etc.each positioned between the upper and inner edges 23 ₁, 23 ₂, etc. ofadjacent blades 2 ₁, 2 ₂, etc. The edges 23 ₁, 23 ₂, etc. of the blades2 ₁, 2 ₂, etc. are, for their part, engaged between the elements 41, 42,43, etc. that form the crown 4.

The band 6, like the crown 4, comprises nine elements. In FIG. 3, afirst element 61 is positioned between two other elements 62 and 63 ofthe band. This element is separated from the elements 62 and 63respectively by lower and outer edges 24 ₁ and 24 ₂ of the first blade 2₁ and of the second blade 2 ₂.

It may be noted that the upper and inner edge 23 ₁ or 23 ₂ of each ofthe two blades 2 ₁ and 2 ₂ lies flush with the exterior surface of thecrown 4 which surface is formed by the respective upper surfaces 41 ₁,42 ₁, 43 ₁, etc. of the elements 41, 42, 43 and equivalent. Likewise,the lower and outer edge 24 ₁ or 24 ₂ of each of these two blades liesflush with the exterior surface of the band 6 which surface is formed bythe respective exterior surfaces 61 ₁, 62 ₁, 63 ₁, etc., of the elements61, 62, 63 and equivalent.

The crown elements 41, 42 and 43 and the band elements 61, 62 and 63 aresecured to the adjacent blades by welding. This method is advantageouslyperformed via an exterior route, in the region where the edge of a bladelies flush with an exterior surface of a crown or band element. Thisthen avoids having welded connections between these bodies on the insideof the runner and, more specifically, in the hydraulic passages definedbetween two blades.

To do this, and as depicted in FIG. 3 which is a section while weldingis in progress, edges 41 ₂ and 41 ₃ of the element 41 which respectivelyadjoin the blades 2 ₁ and 2 ₂ are bevelled, so that with the edges 23 ₁and 23 ₂ they create dihedral angles that accommodate the weld strips.These edges thus define chamfers. A weld strip is visible in FIG. 3,where the element 41 and the blade 2 ₁ meet, and bearing the reference9.

In the second, third and fourth embodiments of the invention which havebeen depicted in FIGS. 4 to 7, elements similar to those of the firstembodiment bear the same references.

FIGS. 4 and 5 are enlargements in the region of the weld between a blade2 ₁ and two band elements 61 and 63. It should be noted that the regionof a weld between a blade and a crown element is similar.

In order to reduce stresses in this type of connection, right-angledconnections between the blade and the adjacent band are avoided. To dothis, provision is made for fillets to be created in each blade.

FIG. 4 depicts two fillets 25 which are formed in the lower part of ablade 2 ₁ in a portion located above two band elements 61 and 63. Thecentral part of the blade has a first thickness e₁ which issubstantially smaller than the thickness e₂ of the lower and outer edge24 ₁ of the blade 2 ₁ which is engaged between the elements 61 and 63 soas to lie flush with the exterior surfaces 61 ₁ and 63 ₁. The fillets 25are substantially symmetric with respect to a median axis Y-Y of theblade 2 ₁.

To manufacture the blade 2 ₁, the operator produces fillets 25 in asheet of thickness e₂ by machining this sheet. However, the productionof such fillets entails the use of a substantial amount of materialintended to be removed by this machining process.

Hence, by way of an alternative which has been depicted in FIG. 5, it isproposed that use be made of a blade 2 ₁ of thickness e₃ substantiallyidentical to the thickness e₁ of the blade of the second embodiment. Twofillets 26 formed on the lower part of the blade, are machined directlynear the lower and outer edge 24 ₁ of this blade 2 ₁ engaged between twoelements 61 and 63 of the band. These fillets 26 are positionedsubstantially symmetrically with respect to the median axis Y-Y of thecross section of the blade 2 ₁. These fillets correspond to lateralfillets created in the blade 2 ₁ in such a way that they define alocalized narrowing near the region for welding. It thus becomespossible to source only a sheet of limited nominal thickness e₃.

FIGS. 6 and 7 depict the runner 1, comprising nine subassemblies, threeof which are visible in FIG. 7, referenced 11, 12 and 13. The firstsubassembly 11 comprises a first crown part 114 and a first band part116 which are connected by a blade 112. The three parts 112, 114 and 116may be cast or welded together to form a one-piece element that can befixed to other elements of the same type, using welding.

Similarly, the subassemblies 12 and 13 respectively comprise a secondcrown part 124 and a third crown part 134 together with a second bandpart 126 and a third band part 136. The parts 124 and 126 and the parts134 and 136 are each respectively connected by a blade 122 and a blade132 through casting or by welding.

Each of these subassemblies 11, 12 and 13 has a cross section in theshape of a lying-down U.

The parts 114 and 116 each comprise an edge 114 ₁ and 116 ₁ respectivelyfacing an upper and inner edge 132 ₁ and a lower and outer edge 132 ₂ ofthe blade 132.

Likewise, the parts 124 and 126 each comprise an edge 124 ₁ and 126 ₁respectively facing an upper and inner edge 112 ₁ and a lower and outeredge 112 ₂ of the blade 112.

It may also be noted that the blade 122 comprises an upper and inneredge 122 ₁ and a lower and outer edge 122 ₂.

The two crown and band parts of each of the subassemblies 11, 12 and 13are respectively provided with an upper surface 114 ₂, 116 ₂, 124 ₂, 126₂, 134 ₂ and 136 ₂.

Thus, the edges of the blades 112, 122 and 132 are engaged between twocrown or band elements. In other words, each of the lower and upperedges of the corresponding blade lies flush with the upper surface ofthe crown and of the adjacent band.

The edges 114 ₁, 124 ₁, 116 ₁ and 126 ₁ are mitered to create, with theedges 132 ₁, 112 ₁, 132 ₂ and 112 ₂ respectively, dihedral angles toaccept weld strips which have not been depicted. In other words, theseedges are chamfered.

This modular approach means that the subassembly 11 can be secured bothto the subassembly 12 and to the subassembly 13 by a welding methodtermed exterior. In other words, there is no need to enter the runner 1,namely to get in between the crown and the band in order to perform thewelding operations aimed at joining the parts of the crown and of theband of a first subassembly to the corresponding parts of an adjacentsecond subassembly.

Moreover, conveying the elements 2 ₁, 2 ₂, 41, 42, 43, 61, 62, 63, etc.or the subassembles 11, 12, 13 and equivalent that make up the runner tothe site at which it will be used is appreciably improved in terms oflead times, making it possible to optimize costs.

It should be noted that the fillets depicted in FIGS. 4 and 5 can alsobe produced in the cast blades 112, 122 and 132.

By way of nonlimiting examples, the welding process used with theinvention may be electron beam welding or laser welding.

Furthermore, it is possible to conceive of a runner comprising a numberof crown elements and/or band elements other than nine thereof.

1-9. (canceled)
 10. A Francis-type runner for a hydraulic machine,comprising: a band with symmetry of revolution about a central axis ofthe runner, a crown with symmetry of revolution about the axis, and aplurality of blades extending between the crown and the band, whereinthe runner comprises at least two elements at least partially definingthe band and/or the crown, and wherein at least one edge the twoelements defining the band and/or the crown.
 11. The runner as claimedin claim 10, wherein the lower edge and/or the upper edge of at leastone blade lies flush with the exterior surface of the band and/or of thecrown.
 12. The runner as claimed in claim 10, wherein the runnercomprises at least two band elements and two crown elements, eachelement being fixed between two adjacent blades by welding.
 13. Therunner as claimed in claim 10, wherein the runner comprises at least onefirst subassembly defined by a first part of the band and a first partof the crown, the two parts being connected to a first blade, the firstsubassembly being cast, and a second subassembly, defined by a secondpart of the band and a second part of the crown, the two parts beingconnected to a second blade, the second subassembly being cast andwelded to the first subassembly.
 14. The runner as claimed in claim 10,wherein at least one of the blades comprises two lateral fillets facingone another and positioned near at least one edge for welding to theband and/or to the crown.
 15. The runner as claimed in claim 14, whereinthe lateral fillets are machined in the blade.
 16. The runner as claimedin claim 14, wherein the lateral fillets define a local narrowing.
 17. Ahydraulic machine, wherein it comprises a runner as claimed in claim 10.18. A method of assembling a runner, comprising the following steps: A)manufacturing band elements and/or crown elements, and B) assembling theband elements and/or crown elements with at least one blade by weldingand/or through casting, with at least one edge of one blade beingengaged between two band elements and/or two crown elements